As stated above, the main reasons why some application implementers (like the original NFS design team) used UDP was because of it's speed and low overhead. As TCP implementations improved over the years, most applications have switched to using TCP but some still offer a UDP variant.

SNMP Defaults | Ports | TCP vs UDP UDP is faster than TCP because it does not order packets (which can be done by the application layer), and it is a connection-less protocol. UDP is actually better suited for repetitive, low-priority functions like alarm monitoring. Therefore, typically, SNMP uses UDP port 161 and UDP port 162. Note: Agents use UDP 161, while the manager uses Why does DNS use UDP? - ClouDNS Blog Why does DNS use UDP? As you just read, the UDP is unreliable but a lot faster than TCP, but don’t panic just yet. DNS requests are very tiny, so they have no problems fitting into the UDP segments. It doesn’t use a time-consuming three-way hand-shake procedure to start the data transfer like TCP does. Why is UDP needed? - Hewlett Packard Enterprise Community

TCP vs UDP. Which to use? | NordVPN - YouTube

The reason why UDP+custom protocol for delivery-critical packets does magic on most games is that, there are times when it could be "okay" if you lose some packet (just for. e.g. secondary non-critical events to complete game play), there are also times where its "not at all okay" to lose some data for e.g cursor movement etc. Why is TCP more secure than UDP? - Information Security Personally if I had a use case that would be better suited for UDP, I would use UDP and secure it with protocols that are designed for security. – TheJulyPlot Jul 20 '17 at 15:28 Since integirty is by definition a pillar of security and the greater attack surface of UDP mainly consists of attacking integrity by spoofing packets then I guess Solved: VOIP - TCP OR UDP? - Cisco Community

That is why we decided to tweak the network to see if the end-user experience would be affected with UDP or with TCP protocol. Second experiment: UDP vs TCP on 15% packet loss network Here we can see the results of the voice quality in a network with 15% of packet loss injected.

UDP is stateless, TCP isn't, but TCP has many predefined properties that didn't suite NFS, or rather that NFS wanted to govern the specifics. In particular, when TCP is doing packet transfers, it does govern timeouts, etc. With UDP, you lose the overheads that you don't particularly want any way. SNMP Defaults | Ports | TCP vs UDP